JPWO2007145177A1 - Pneumatic tire - Google Patents

Abstract

The pneumatic tire of the present invention improves wet performance. A first main groove 2 extending in the tire circumferential direction TC is provided on the tread surface 1, and a first lateral groove 7 extending from the first main groove 2 toward the outer side in the tire width direction beyond one tire ground contact end TX1. Is a pneumatic tire in which a block 8 is formed by the first main grooves 2 and the first lateral grooves 7 at a predetermined pitch in the tire circumferential direction TC. An inner groove portion 7A in which the first lateral groove 7 extends from the first main groove 2 toward the outer side in the tire width direction while gradually increasing the groove width to the middle portion of the first lateral groove 7, and from the gradually increased inner groove portion 7A to the tire width direction The outer groove portion 7B extends beyond one tire ground contact end TX1 while gradually reducing the groove width toward the outside. One circumferential narrow groove 5 extending in the tire circumferential direction TC and having a groove width narrower than that of the first main groove 2 is disposed at a boundary position between the inner groove portion 7A and the outer groove portion 7B.

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire capable of improving wet performance.

  Conventionally, various pneumatic tires have been proposed in which tire performance is improved by devising and arranging main grooves extending in the tire circumferential direction and lateral grooves extending in the tire width direction on the tread surface ( For example, see Patent Documents 1 and 2).

However, further improvements in tire performance are required due to the recent increase in awareness of safety during vehicle travel. In particular, accidents when driving on wet roads in rainy weather can lead to major accidents, so there is a strong demand for proposals for improvement techniques.
Japanese Unexamined Patent Publication No. 7-285302 Japanese Unexamined Patent Publication No. 8-230415

  An object of the present invention is to provide a pneumatic tire capable of improving wet performance.

  In order to achieve the above object, the present invention provides a first main groove extending in the tire circumferential direction on the tread surface, and extends beyond the one tire ground contact edge from the first main groove toward the outer side in the tire width direction. In the pneumatic tire in which the existing first lateral grooves are arranged at a predetermined pitch in the tire circumferential direction and a block is formed by the first main grooves and the first lateral grooves, the first lateral grooves are spaced from the first main grooves to the tire width. An inner groove extending while gradually increasing the groove width toward the middle of the first lateral groove toward the outer side in the direction, and exceeding the tire ground contact edge while gradually decreasing the groove width from the gradually increased inner groove toward the outer side in the tire width direction. An outer groove portion extending in a circumferential direction, and a circumferential narrow groove extending in the tire circumferential direction and having a groove width narrower than the first main groove is disposed at a boundary position between the inner groove portion and the outer groove portion. Provide pneumatic tires.

  According to the present invention described above, the water in the first lateral groove during wet road traveling can be more effectively guided to the boundary position between the inner groove portion and the outer groove portion than the lateral groove having the same groove width. It can discharge efficiently by the arranged circumferential narrow groove. Accordingly, it is possible to improve the handling stability when traveling on a wet road surface.

  If the main groove similar to the first main groove is disposed in place of the circumferential narrow groove to improve drainage, the tread rigidity in the region outside the tire width direction from the first main groove is reduced, and when driving on a dry road surface Although the steering stability is reduced, such a problem does not occur because of the circumferential narrow groove.

FIG. 1 is a partial development view of a tread surface showing an embodiment of a pneumatic tire of the present invention. FIG. 2 is a partially enlarged sectional view taken along the first lateral groove of FIG. FIG. 3 is an enlarged cross-sectional view of the first main groove. FIG. 4 is an enlarged cross-sectional view of the second and third main grooves. FIG. 5 is a partial development view of a tread surface showing another embodiment of the pneumatic tire of the present invention. FIG. 6 is a partially enlarged cross-sectional view when cut along the narrow lateral groove of FIG. FIG. 7 is a partial development view showing another pattern of the vehicle inner region of the tread surface. FIG. 8 is a partial development view of a tread surface of a reference tire in Examples 2 and 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread surface 1A Vehicle inside area | region 1B Vehicle outside area | region 2 1st main groove 3 2nd main groove 4 3rd main groove 5 Circumferential thin groove 6 Center rib 7 1st horizontal groove 7A Inner groove part 7B Outer groove part 8 Block 9 2nd horizontal groove DESCRIPTION OF SYMBOLS 10 Sub lateral groove 11 Block 12 3rd lateral groove 13 Block 14 Narrow groove 16 Bottom raising part 21 Narrow lateral groove GS Groove wall surface TC Tire circumferential direction TE Tire equatorial plane TX1, TX2 Tire grounding edge W Tire grounding width d1 Groove depth of first lateral groove

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows an embodiment of the pneumatic tire of the present invention. The pneumatic tire is mounted on the vehicle with the left side of FIG. 1 being the vehicle inner side, and the vehicle mounting direction is designated. The tread surface 1 has a vehicle inner side region 1A on the left side of the tire equator surface TE and a vehicle outer side region 1B on the right side of the tire equator surface TE.

  The tread surface 1 is provided with three main grooves extending linearly continuously in the tire circumferential direction TC. The three main grooves include one first main groove 2 disposed in the vehicle outer region 1B of the tread surface 1, one second main groove 3 disposed in the vehicle inner region 1A of the tread surface 1, and one The third main groove 4 is constituted. The first main groove 2 is provided on the tire equatorial plane TE side of the vehicle outside region 1B. The second main groove 3 is disposed on the tire equatorial plane TE side of the vehicle inner region 1A. The third main groove 4 is disposed on the outer side in the tire width direction from the second main groove 3, and the outer side in the tire width direction from the third main groove 4 is a shoulder region 1 AS in the vehicle inner region 1 A of the tread surface 1.

  The vehicle outer region 1B of the tread surface 1 has one groove extending outwardly in the tire width direction from the first main groove 2, narrower than the first main groove 2, and continuously extending in the tire circumferential direction TC. The circumferential narrow groove 5 is disposed. The outer side in the tire width direction from the circumferential narrow groove 5 is a shoulder region 1BS in the vehicle inner region 1A of the tread surface 1. By providing not the main groove but the circumferential narrow groove 5 in the vehicle outer region 1B of the tread surface 1, the tread rigidity in the region on the outer side in the tire width direction from the main groove 4 of the vehicle outer region 1B is increased.

  The main grooves 2, 3 and 4 referred to here are grooves having a groove width of 10 mm to 20 mm and a groove depth of 6 mm to 10 mm. Moreover, the circumferential direction fine groove 5 said here is a groove | channel with a groove width of 2 mm-8 mm, and a groove depth of 2 mm-8 mm.

  A center rib 6 extending continuously in the tire circumferential direction TC is formed between the main grooves 2 and 3. The center rib 6 ensures the tread rigidity of the center portion where the tire equatorial plane TE is located, and improves the handling stability on the dry road surface.

  In the vehicle outer region 1B of the tread surface 1, the first lateral grooves 7 extending in the tire width direction are arranged at a predetermined pitch larger than the pitch of the third lateral grooves 12 described later in the tire circumferential direction TC. The first lateral groove 7 extends from the first main groove 2 toward the outer side in the tire width direction, beyond the circumferential narrow groove 5, and further beyond one tire ground contact end TX1 to the other design end 1X1 of the tread surface 1. is doing. By extending the first lateral groove 7 to the one design end 1X1 in this way, the protrusions of the mold for forming the first lateral groove 7 can be easily removed from the vulcanized tire.

  The groove area ratio of the first lateral groove 7 in the tread surface region between the first main groove 2 and one tire ground contact end TX1 is in the tread surface region between the third main groove 3 and the other tire ground contact end TX2. The groove area ratio of the third lateral groove 12 is smaller. The groove width of the first horizontal groove 7 is wider than the groove width of the third horizontal groove 12. A block 8 is formed by a first main groove 2, a first lateral groove 7, and a circumferential narrow groove 5 in the vehicle outer side region 1 </ b> B outside the first main groove 2 in the tire width direction.

  Each first lateral groove 7 is circumferentially located in the middle of the first lateral groove 7 while being inclined from the first main groove 2 toward the outer side in the tire width direction toward one side of the tire circumferential direction TC (the lower side in FIG. 1). An inner groove 7A extending to the narrow groove 5 and one tire while inclining from the inner groove 7A (circumferential narrow groove 5) toward the outer side in the tire width direction toward the other side (upper side in FIG. 1) of the tire circumferential direction TC The outer groove 7B extends to the one design end 1X1 beyond the grounding end TX1. By extending the first lateral groove 7 in this manner, the noise (pattern noise) that the edge (leading edge) of the block 8 facing the first lateral groove 7 hits the road surface is reduced.

  The groove width of the inner groove portion 7A gradually increases from the first main groove 2 side toward the outer circumferential groove 5 toward the outer side in the tire width direction. The outer groove portion 7B is gradually narrowed toward the outer side in the tire width direction from the circumferential narrow groove 5 to a position exceeding one tire ground contact end TX1, and the first lateral groove 7 is on the first main groove 2 side. The groove width gradually increases toward the outer side in the tire width direction, and then gradually decreases toward the outer side in the tire width direction with the circumferential narrow groove 5 arranged at the boundary position between the inner groove portion 7A and the outer groove portion 7B.

  Although the inner groove portion 7A is formed in an arc shape having a large radius of curvature that is convex on one side in the tire circumferential direction TC in FIG. 1, it may be linear. The outer groove portion 7B is formed in an arc shape having a large radius of curvature that is convex on the other side in the tire circumferential direction TC, but may be formed in a straight line like the inner groove portion 7A. The groove width of the first lateral groove 7 is gradually increased depending on the tire size and the like within a range of 5 mm to 10 mm in the portion of the first lateral groove 7 located between the first main groove 2 and one tire ground contact end TX1. It can be gradually reduced.

  Between the main grooves 3 and 4, second lateral grooves 9 extending in the tire width direction and sub-lateral grooves 10 having a shorter length than the second lateral grooves 9 are alternately arranged at a predetermined pitch in the tire circumferential direction TC. The second lateral groove 9 extends linearly from the second main groove 3 to the third main groove 4 while inclining to one side in the tire circumferential direction TC. A block 11 is formed by the main grooves 3 and 4. The second lateral grooves 9 are arranged at a pitch larger than the pitch of the third lateral grooves 12 to be described later, and the formed block 11 is longer in the tire circumferential direction than the later-described block 13 formed by the third lateral grooves 12, The rigidity in the tire circumferential direction of the block 11 is increased. In the embodiment shown in FIG. 1, the second lateral grooves 9 are arranged at twice the pitch of the third lateral grooves 12.

  The sub transverse groove 10 is inclined in the same direction as the second transverse groove 9, one end communicates with the third main groove 4, and the other end does not communicate with the second main groove 3 and is located in the block 11. Instead of that, the sub-lateral groove 10 may extend to the second main groove 3. By extending the horizontal grooves 9 and 10 so as to be inclined in this manner, the noise (pattern noise) of the block 9 facing the horizontal grooves 9 and 10 (leading edge) hitting the road surface is reduced. The second lateral groove 9 and the secondary lateral groove 10 are linearly extended in FIG. 1, but may be formed in an arc shape having a large radius of curvature instead.

  In the shoulder region 1AS of the vehicle inner region 1A of the tread surface 1, third lateral grooves 12 extending in the tire width direction are arranged at a predetermined pitch in the tire circumferential direction TC. The third lateral groove 12 extends from the third main groove 4 toward the outer side in the tire width direction while being inclined to one side in the tire circumferential direction TC and beyond the other tire ground contact end TX2 to the other design end 1X2 of the tread surface 1. It is extended. A block 13 is formed by the third main groove 4 and the third lateral groove 12 in the shoulder region 1AS.

  Thus, by extending the third lateral groove 12 in an inclined manner, the sound (pattern noise) of the block 13 facing the third lateral groove 12 (leading edge) hitting the road surface is also reduced. Further, by extending the third lateral groove 12 to the other design end 1X2, it is possible to easily remove the protruding portion of the mold for forming the third lateral groove 12 from the vulcanized tire. The main body portion 12A of the third lateral groove 12 can be extended in a linear shape or an arc shape having a large radius of curvature close to a straight line.

  In the center portion of the center rib 6, one narrow groove 14 extending in a straight line continuously in the tire circumferential direction TC is provided. As a result, the tread surface 1 formed in a circular arc shape in the section of the narrow groove 14 is easily bent so that a desired arc-shaped profile can be obtained when the air pressure is filled. The narrow groove 14 here is a groove having a groove width of 2 mm to 4 mm and a groove depth of 2 mm to 3 mm. The narrow groove 14 may not be provided when it is desired to increase the rigidity of the center rib 6 as much as possible. In FIG. 1, reference numeral 15 denotes auxiliary grooves arranged at both ends of the center rib 6.

  According to the present invention described above, the groove width of the first lateral groove 7 extending from the first main groove 2 toward the outer side in the tire width direction beyond the one tire ground contact end TX1 is gradually increased toward the outer side in the tire width direction. Then, by gradually reducing the structure, the tire circumferential direction length of the block 8 formed by the first lateral grooves 7 is changed in the tire width direction, and the water in the first lateral grooves 7 is drained when contacting the road surface. A surface pressure difference that leads to the boundary position between the inner groove portion 7A and the outer groove portion 7B can be generated in the block 8. Therefore, the water in the first lateral groove 7 is effectively guided to the boundary position between the inner groove portion 7A and the outer groove portion 7B than the lateral groove having the same groove area as that of the first lateral groove 7 and having a constant groove width, and is used as the boundary position. It can discharge | emit with the circumferential direction thin groove 5 arrange | positioned. Accordingly, it is possible to improve the handling stability when traveling on a wet road surface.

  When the main groove similar to the first main groove 2 is arranged in place of the circumferential narrow groove 5 to improve drainage, the tread rigidity in the outer region in the tire width direction from the first main groove 2 in the vehicle outer region 1B is increased. However, since it is the circumferential narrow groove 5, such a problem does not occur.

  In the above embodiment, the first main groove 2 of the vehicle outer side region 1B of the tread surface 1 is in the range of 8% to 25% of the tire ground contact width W from the tire equator surface TE toward the outer side in the tire width direction (vehicle outer side). While arranged in a certain region 1Bx, the second main groove 3 in the vehicle inner region 1A of the tread surface 1 is 8% to 25% of the tire ground contact width W from the tire equator surface TE toward the outer side in the tire width direction (vehicle inner side). It is preferable to arrange in the region 1Ax in the range of% from the viewpoint of steering stability on a dry road surface and drainage.

  When the main grooves 2 and 3 are located on the inner side in the tire width direction from the regions 1Ax and 1Bx, the rib width of the center rib 6 becomes narrow, and sufficient rib rigidity cannot be secured. Steering stability is reduced. Further, since the main grooves 2 and 3 are close to the tire equatorial plane TE, the air column resonance due to the main grooves 2 and 3 is increased. When the main grooves 2 and 3 are located outside the regions 1Ax and 1Bx in the tire width direction, the drainage performance is deteriorated. Preferably, the first main groove 2 and the second main groove 3 are positioned within the range of 10% to 20% of the tire ground contact width W from the tire equatorial plane TE in order to improve the handling stability and drainage on the dry road surface. Good in terms of balance.

  Although the second main groove 3 and the third main groove 4 have the same groove width in FIG. 1, the groove widths may be different. The groove width of the first main groove 2 is at least 110% of the groove width of the main groove with the narrower groove width among the main grooves 3 and 4, and the groove width of the first main groove 2 is thus reduced. By widening, the high drainage by the 1st main groove 2 arrange | positioned in the vehicle outer side area | region 1B of the tread surface 1 is ensured. When the groove width of the first main groove 2 is narrower than 110%, the drainage performance is lowered, and the steering stability on the wet road surface is lowered. The upper limit value of the groove width of the first main groove 2 is preferably 130% or less of the groove width of the narrower main groove from the viewpoint of driving stability on the dry road surface.

  As described above, the first lateral grooves 7 are preferably arranged at a pitch larger than the pitch of the third lateral grooves 12 in the tire circumferential direction TC. In FIG. 1, the pitch of the first lateral grooves 7 is twice the pitch of the third lateral grooves 12. By arranging the first lateral grooves 7 at a pitch larger than that of the third lateral grooves 12 in this way, the circumferential rigidity of the block 8 formed in the vehicle outer region 1B of the tread surface 1 is disposed in the vehicle inner region 1A of the tread surface 1. Thus, it is possible to increase the steering stability when traveling on a dry road surface during cornering. Moreover, the ground contact area of each block 8 in the vehicle outer side area | region 1B of the tread surface 1 can be enlarged, and the ground contact property at the time of wet road surface travel can be improved.

  Further, since a greater shearing force acts on the vehicle outer side region 1B than on the vehicle inner side region 1A of the tread surface 1 during cornering or the like, uneven wear occurs in which the block in the vehicle outer side region 1B wears faster than the block in the vehicle inner side region 1A. However, by increasing the circumferential rigidity of the block 8 in the vehicle outer region 1B as compared with the block 13 in the vehicle outer region 1B, the progress of wear of the block 8 in the vehicle outer region 1B is delayed and uneven wear is suppressed. be able to. Moreover, since the pitch number of the 1st horizontal groove 7 decreases from the pitch number of the 3rd horizontal groove 12, the noise resulting from a pitch number can be reduced.

  As shown in FIG. 2, the first lateral groove 7 is preferably configured such that the groove depth in the boundary region BR between the inner groove portion 7A and the outer groove portion 7B is shallower than the other regions. That is, the bottom raised portion 16 is provided at the groove bottom of the first lateral groove 7 by partially reducing the depth of the first lateral groove 7 in the boundary region BR.

  As a result, the rigidity of the portion 8a of the block 8 adjacent to the intersection of the circumferential narrow groove 5 and the first lateral groove 7 can be increased, so that the block portion 8a is prevented from falling when cornering on the dry road surface. , Can improve steering stability. Moreover, since the groove volume of the 1st horizontal groove 7 reduces by making the 1st horizontal groove 7 partially shallow, the noise at the time of the passage resulting from the air column resonance of the 1st horizontal groove 7 can be reduced.

  The groove depth d1 of the first lateral groove 7 where the bottom raised portion 16 is located is preferably 2 mm to 5 mm from the viewpoint of drainage and block rigidity. If the groove depth d1 of the first lateral groove 7 is shallower than 2 mm, water flowing from the first lateral groove 7 to the circumferential narrow groove 5 is hindered by the bottom raising portion 16, so that the drainage performance is lowered. When the groove depth d1 of the first lateral groove 7 is deeper than 5 mm, it is difficult to effectively increase the rigidity of the block portion 8a. The groove depth of the first lateral groove 7 in the portion where the bottom raised portion 16 is located between the first main groove 2 and the one tire ground contact end TX1 can be in the range of 3 mm to 7 mm.

  The first lateral grooves 7 are preferably inclined and extended as described above, because the sound of the edges (leading edges) of the blocks 8 facing the first lateral grooves 7 can be reduced. You may make it extend along a tire width direction, without doing. More preferably, as shown in FIG. 1, the first lateral groove 7 has the inner groove portion 7A inclined on one side in the tire circumferential direction TC and the outer groove portion 7B inclined on the other side in the tire circumferential direction TC, or the groove portions 7A and 7B. The groove portions 7A and 7B are not inclined in the same direction with respect to the tire circumferential direction TC in order to reduce noise during passage due to air column resonance in the first lateral groove 7. It's okay.

  When the first lateral groove 7 is inclined, the steering angle on the dry road surface is such that the inclination angle θ1 of the inner groove portion 7A of the first lateral groove 7 with respect to the tire circumferential direction TC is in the range of 30 ° to 85 ° on the acute angle side, This is good in terms of drainage during cornering and noise caused by the edges of the block 8. When the inclination angle θ1 of the inner groove portion 7A is smaller than 30 °, the steering stability on the dry road surface decreases due to the decrease in the rigidity of the acute corner portion 8a of the block 8. If the inclination angle θ1 of the inner groove portion 7A is greater than 85 °, the drainage capacity at the time of cornering is lowered, and the sound of the edge of the block 8 hitting the road surface increases. The inclination angle θ2 of the outer groove portion 7B of the first lateral groove 7 with respect to the tire circumferential direction TC is preferably set to a range of 30 ° to 85 ° on the acute angle side for the same reason as described above. The inclination angle θ2 of the outer groove portion 7B referred to here is an inclination angle of the portion 7Bm of the outer groove portion 7B located in the region from the circumferential narrow groove 5 to one tire ground contact end TX1.

  For the same reason as described above, the inclination angle α1 of the second lateral groove 9 with respect to the tire circumferential direction TC and the inclination angle α2 of the third lateral groove 12 with respect to the tire circumferential direction TC are within the range of 30 ° to 85 ° on the acute angle side. To preferred. The inclination angle α2 of the third lateral groove 12 referred to here is the inclination angle of the portion 12m of the third lateral groove 12 located in the region from the third main groove 4 to the other tire ground contact edge TX2.

  When the inner groove portion 7A and the outer groove portion 7B, the second lateral groove 9, and the third lug groove 12 of the first lateral groove 7 extend in an arc shape, the inclination angle is as follows.

  In the case of the inner groove portion 7A of the first lateral groove 7, the inclination angle θ1 connects the inner end of the inner groove portion 7A communicating with the first main groove 2 and the outer end of the inner groove portion 7A communicating with the circumferential narrow groove 5 at the groove center. The inclination angle with respect to the straight tire circumferential direction TC.

  In the case of the outer groove portion 7B of the first lateral groove 7, the inclination angle θ2 connects the inner end of the outer groove portion 7B communicating with the circumferential narrow groove 5 at the groove center and the portion of the outer groove portion 7B in contact with one tire ground contact end TX1. The inclination angle with respect to the straight tire circumferential direction TC.

  In the case of the second horizontal groove 9, the inclination angle α 1 is a straight line connecting the inner end of the second horizontal groove 9 communicating with the second main groove 3 and the outer end of the second horizontal groove 9 communicating with the third main groove 4 at the groove center. Is an inclination angle with respect to the tire circumferential direction TC.

  In the case of the third lateral groove 12, the inclination angle α2 is a straight line connecting the inner end of the third lateral groove 12 communicating with the third main groove 4 at the groove center and the portion of the third lateral groove 12 in contact with the other tire ground contact end TX2. The inclination angle with respect to the tire circumferential direction TC.

  As shown in FIG. 1, the auxiliary lateral groove 10 is preferably not extended to the second main groove 3 from the viewpoint of driving stability on a dry road surface. Alternatively, the sub-lateral groove 10 may extend from the second main groove 3 to the outer side in the tire width direction and not communicate with the third main groove 4. The main groove can be extended while inclining in the tire circumferential direction TC. In this case, the length L1 of the sub-lateral groove 10 in the tire width direction is 20% or more of the length L2 in the tire width direction between the main grooves 3 and 4 from the viewpoint of drainage, and from the viewpoint of steering stability on the dry road surface. It is preferable to make it 80% or less of the length L2 in the tire width direction.

  As shown in FIGS. 3 and 4, the groove wall surface GS of the main grooves 2 to 4 is an intersection CP between the tread surface 1 having an arcuate cross section and the groove wall surface GS in a cross section when the tire is cut along a plane passing through the tire axis. Is inclined with respect to a straight line (tire normal line) TN perpendicular to the tangent line TL passing through the intersection point CP, while increasing the grip force when traveling on the tri road surface in the vehicle outer region 1B. In order to enhance drainage performance in the inner region 1A, the inclination angle β1 with respect to the straight line TN of the groove wall surface GS of the first main groove 2 is set to the straight line TN of the groove wall surface GS of the second and third main grooves 3 and 4. It is preferable to make it larger than the inclination angle β2. Thereby, the steering stability on the dry road surface and the wet road surface can be further improved. The inclination angle β1 can be in the range of 20 ° to 50 °, and the inclination angle β2 can be in the range of 10 ° to 40 °. In addition, when the corner portion Ca of the block sandwiched between the tread surface 1 and the groove wall surface GS is chamfered, the tire normal TN is obtained in a state where the chamfer is not chamfered.

  FIG. 5 shows another embodiment of the pneumatic tire of the present invention. The pneumatic tire of FIG. 5 has one narrow lateral groove 21 that is narrower than the first lateral groove 7 and extends in the tire width direction between the two first lateral grooves 7 adjacent to each other in the tire circumferential direction TC. Other than the arrangement, it has the same configuration as the pneumatic tire of FIG. 1 described above. Accordingly, the same components are denoted by the same reference numerals, and redundant description is omitted.

  The narrow lateral grooves 21 are located at substantially the center between the two first lateral grooves 7, and the narrow lateral grooves 21 and the first lateral grooves 7 are alternately arranged at the same pitch as the third lateral grooves 12 in the tire circumferential direction. The narrow lateral groove 21 includes an inner narrow groove portion 21A extending from the first main groove 2 toward the outer side in the tire width direction toward the circumferential narrow groove 5 while being inclined to one side in the tire circumferential direction TC, and an inner narrow groove portion 21A (circumferential groove). The outer narrow groove portion 21B that extends from the direction narrow groove 5) toward the other side in the tire circumferential direction TC toward the outer side in the tire width direction and extends to one design end 1X1 beyond one tire ground contact end TX1. ing.

  The inner narrow groove portion 21A is formed in the block 8 between the first main groove 2 and the circumferential narrow groove 5, and the outer narrow groove portion 21B is formed in the block 8 in the shoulder region 1BS outside the circumferential narrow groove 5 in the tire width direction. Each block 8 is divided into two blocks 8A and 8B by a narrow lateral groove 21. The narrow lateral groove 21 has a substantially constant width, and the groove width is 1 mm to 4 mm, preferably 1 mm to 3 mm.

  In the tread pattern of FIG. 1, if the first lateral grooves 7 are provided at the same pitch as the third lateral grooves 12 to further improve the drainage, the tire circumferential rigidity of the block 8 is lowered, thereby causing a dry road surface at cornering. The steering stability of the vehicle deteriorates, and uneven wear occurs in which the block in the vehicle outer region 1B wears earlier than the block in the vehicle inner region 1A. Therefore, in the embodiment of FIG. 5, between the two first lateral grooves 7 adjacent to each other in the tire circumferential direction TC, one narrow lateral groove 21 narrower than the first lateral groove 7 is disposed, By arranging the first lateral grooves 7 alternately at the same pitch as the third lateral grooves 12 in the tire circumferential direction TC, the collapse of one block 8A (or 8B) in the tire circumferential direction TC is caused by the other block 8B (or 8A). Can be suppressed. Therefore, with respect to the tire having the tread pattern of FIG. 1, it is possible to suppress a decrease in steering stability on the dry road surface during cornering while further improving drainage by the narrow lateral grooves 21. Further, it is possible to improve the occurrence of uneven wear in which the blocks 8A and 8B in the vehicle outside region 1B wear out earlier than the block 13 in the vehicle inside region 1A.

  As shown in FIG. 6, the narrow lateral groove 21 is provided with a bottom-up portion 22 at the bottom of the groove in the region BL intersecting with the circumferential narrow groove 5, and the groove depth of the narrow lateral groove 21 is partly in other regions. It is better to make it shallower. As a result, the rigidity of the corners of the blocks 8A and 8B adjacent to the intersection of the circumferential narrow groove 5 and the narrow lateral groove 21 can be increased, so that the corners of the blocks 8A and 8B are not cornered on the dry road surface. It is possible to suppress the falling and improve the handling stability on the dry road surface. Moreover, it contributes to the improvement of the above-mentioned uneven wear resistance.

  The groove depth d2 of the narrow lateral groove 21 in which the bottom raised portion 22 is located is preferably 1 mm to 5 mm from the viewpoint of drainage and block rigidity. If the groove depth d of the narrow lateral groove 21 is shallower than 1 mm, the water flowing from the narrow lateral groove 21 to the circumferential narrow groove 5 is obstructed by the bottom raising portion 22, so that the drainage effect by the narrow lateral groove 21 is reduced. If the groove depth d2 of the narrow lateral groove 21 is deeper than 5 mm, it is difficult to effectively increase the rigidity of the corners of the blocks 8A and 8B. The groove depth of the narrow lateral groove 21 in the portion where the bottom raised portion 22 is located between the first main groove 2 and the one tire ground contact edge TX1 can be in a range of 2 mm to 6 mm.

  In the present invention, the first lateral grooves 7 and the circumferential narrow grooves 5 described above are provided in the vehicle outer region 1B of the tread surface 1 as shown in FIG. Although preferable above, the pneumatic tire of the present invention may be one in which the first lateral groove 7 and the circumferential narrow groove 5 described above are arranged in the vehicle inner region 1A of the tread surface 1.

  In the above embodiment, the pneumatic tire in which the vehicle mounting direction is specified has been described. However, in the pneumatic tire according to the present invention having the first lateral groove 7 and the circumferential narrow groove 5 described above, the vehicle mounting direction is specified. A non-pneumatic tire may be used.

  In the present invention, as shown in the above-described embodiment, the third main groove 12 is formed by inclining the third lateral groove 12 to one side (the lower side in FIG. 1) in the tire circumferential direction TC as the inner groove portion 7A of the first lateral groove 7. 4 and extending from the second main groove 3 by inclining the second lateral groove 9 to the other side (upper side in FIG. 1) of the same tire circumferential direction TC as the outer groove portion 7B of the first lateral groove 7. However, as shown in FIG. 6, the third lateral groove 12 may extend from the third main groove 4 toward the outer side in the tire width direction while being inclined toward the other side in the tire circumferential direction TC. 12 may extend so as to incline to one side or the other side in the tire circumferential direction TC. When the third lateral groove 12 is inclined to the other side in the tire circumferential direction TC, the inclination angle α2 ′ of the third lateral groove 12 with respect to the tire circumferential direction TC can be made the same as the inclination angle α2 on the acute angle side.

  Further, as shown in FIG. 7, the second lateral groove 9 may extend from the second main groove 3 while being inclined toward one side of the tire circumferential direction TC toward the outer side in the tire width direction. 9 can also be inclined and extended to one side or the other side of the tire circumferential direction TC. When the second lateral groove 9 is inclined toward one side in the tire circumferential direction TC, the inclination angle α1 ′ of the second lateral groove 9 with respect to the tire circumferential direction TC can be the same as the inclination angle α1 on the acute angle side.

  The present invention can be preferably used particularly for a pneumatic tire for a passenger car, but is not limited thereto, and can also be applied to other pneumatic tires.

  In the present invention, the tire ground contact width W is the maximum load specified by JATPA with a pressure of 220 kPa when the tire is mounted on an applicable rim specified by JATMA (JATMA YEAR BOOK 2006). Measured with a load equivalent to 88% of the capacity applied, and tires for other applications were loaded with air pressure corresponding to the maximum load capacity specified by JATMA and a load corresponding to the maximum load capacity. Measure in state. The tire ground contact ends TX1 and TX2 are the ground contact ends positioned on the outermost side in the tire width direction of the tread surface 1 when the tire contacts the road surface with the tire contact width W. In addition, the inclination angles β1 and β2 of the groove wall surface GS of the main grooves 2 to 4 are measured under the same conditions as the measurement of the tire ground contact width W except that the load is not applied.

  The present invention tire 1 having the same tire size as 245 / 40R18, having the tread pattern shown in FIG. 1, the present invention tire 2 having the same structure as the present invention tire 1 except that a bottom raised portion is provided in the first lateral groove, and the tread A reference tire having the same structure as that of the tire 1 of the present invention was produced, except that the width of the first lateral groove in the vehicle outer region of the surface was made constant.

  In the tires 1 and 2 of the present invention and the reference tire, the groove area ratio of the first lateral grooves in the vehicle outer region of the tread surface is the same, and the groove depths of the first lateral grooves are 5.5 mm. The groove width of the circumferential narrow groove is 2.5 mm and the groove depth is 6.4 mm, which is common to all tires. In the tire 2 of the present invention, the groove depth of the lug groove at the bottom raised portion is 3 mm.

  Each of these tires is assembled to a rim having a rim size of 8.5 J, mounted on a four-wheel drive vehicle (test vehicle) with a displacement of 2000 cc and an air pressure of 220 kPa, and wet steering stability, dry steering stability and When the passing noise evaluation test was performed, the results shown in Table 1 were obtained.

Wet handling stability On the wet road test course, a sensory test of handling stability was conducted by a test driver. The evaluation result is indicated by an index value where the reference tire is 100. The larger this value, the better the wet handling stability.

Dry handling stability On the dry road test course, a test driver conducted a sensory test on handling stability. The evaluation result is indicated by an index value where the reference tire is 100. The larger this value, the better the dry handling stability.

Passing noise On a dry road test course, the test vehicle is run from 100 km / h with inertia, which does not step on the accelerator, and the sound pressure level until it stops is measured, and the measured value is 55 km / h, road surface temperature. It converted into the sound pressure level on 5 degreeC conditions. The converted result is indicated by an index value where the reference tire is 100. The larger this value, the lower the passing noise.

  From Table 1, it can be seen that the tire of the present invention can improve wet steering stability (wet performance). In addition, it can be seen from the tire 2 of the present invention that wet performance can be improved and further passing noise can be improved while improving steering stability when driving on a dry road surface by providing a bottom raised portion with a partially shallow lug groove. .

  The tire size is the same as in Example 1, and the positions of the first main groove in the vehicle outer region of the tread surface and the second main groove in the vehicle inner region of the tread surface and the groove width of the first main groove are as shown in Table 2. Test tires 1 to 9 having the tread pattern shown in FIG.

  In the test tires 1 to 9, the second main groove and the third main groove in the vehicle inner region of the tread surface have the same groove width (16 mm), the inclination angle θ1 of the inner groove portion of the first lateral groove is 45 °, the first The inclination angle θ2 of the outer groove portion of the transverse groove is 80 °, the inclination angle α1 of the second transverse groove is 60 °, the inclination angle α2 of the third transverse groove is 85 °, and the tire width direction length L1 of the auxiliary transverse groove is the tire width direction length L2. It is common to 52%. Further, the groove depth of the first lateral groove, the groove width and the groove depth of the circumferential narrow groove of each test tire are the same as those in the first embodiment.

  These test tires were mounted on a four-wheel drive vehicle with a displacement of 2000 cc in the same manner as in Example 1, and wet steering stability and dry steering stability were evaluated by the method shown in Example 1. Table 2 The results shown are obtained. However, the results of the wet steering stability and the dry steering stability shown in Table 2 are indicated by index values with the tire having the tread pattern shown in FIG. The larger this value, the better the performance.

  From the test tires 2 to 4 in Table 2, the first main groove and the second main groove are disposed in the region located in the range of 8% to 25% of the tire ground contact width from the tire equator plane, respectively, so that wet steering stability is achieved. It can be seen that both (wet performance) and dry handling stability (dry performance) can be increased to 103 or more.

  Further, it can be seen from the test tires 3, 7, and 8 in Table 2 that both wet performance and dry performance can be increased to 103 or more by setting the width of the first main groove in the range of 110% to 130%. .

  Test tires 10 having the tread pattern shown in FIG. 1 and test tires 11 and 12 having a tread pattern shown in FIG.

  In the test tires 11 and 12, the narrow lateral groove has the configuration shown in FIG. 6, the narrow lateral groove has a groove width of 3 mm, the narrow lateral groove has a groove depth of 2 mm at the bottom raised portion, and 4 mm in other regions. In addition, in each test tire, the second main groove and the third main groove in the vehicle inner region of the tread surface have the same groove width (16 mm), and the groove width of the first main groove is 120% of the second main groove. is there. In each of the test tires, the first main groove and the second main groove are located at 25% of the tire ground contact width from the tire equatorial plane. In each test tire, the inclination angles θ1, θ2, α1, α2, the tire lateral direction length L1 of the secondary lateral groove, the groove depth of the first lateral groove, the groove width and the groove depth of the circumferential narrow groove are as in Example 2. The same. In each test tire, the inner groove portion of the first lateral groove gradually increases in the range of 6.5 mm to 10 mm, and the outer groove portion of the first lateral groove gradually decreases in the range of 9.5 mm to 5.5 mm. The inclination angles β1 and β2 of the wall surface of the main groove of each test tire are as shown in Table 3.

  These test tires were mounted on a four-wheel drive vehicle with a displacement of 2000 cc in the same manner as in Example 1, and wet steering stability and dry steering stability were evaluated by the method shown in Example 1. Table 3 The results shown are obtained. The results of wet steering stability and dry steering stability shown in Table 3 are also shown as index values with the tire having the tread pattern shown in FIG. The larger this value, the better the performance.

  From Table 3, the test tire 11 with the narrow lateral groove further improves the steering stability on the wet road surface while suppressing the decrease in the steering stability on the dry road surface to 104 compared to the test tire 10 without the narrow lateral groove. It can be seen that the wet performance can be further improved by suppressing the decrease in the dry performance by arranging the narrow lateral grooves.

  Further, from the test tires 11 and 12, by making the inclination angle β1 of the groove wall surface of the first main groove larger than the inclination angle β2 of the second and third main groove groove wall surfaces, the dry performance and the wet performance can be further improved. Recognize.

  The present invention having the above-described excellent effects can be suitably used for a pneumatic tire used in a vehicle such as a passenger car.

Claims (17)

A first main groove extending in the tire circumferential direction is provided on the tread surface, and a first lateral groove extending beyond one tire ground contact end from the first main groove toward the outer side in the tire width direction is predetermined in the tire circumferential direction. In a pneumatic tire that is arranged at a pitch of, and in which a block is formed by the first main groove and the first lateral groove,
An inner groove extending from the first main groove toward the outer side in the tire width direction toward the middle of the first lateral groove while gradually increasing the groove width, and an outer side in the tire width direction from the gradually increased inner groove An outer groove portion extending beyond the tire ground contact end while gradually reducing the groove width toward the tire, extending in the tire circumferential direction at a boundary position between the inner groove portion and the outer groove portion, and from the first main groove A pneumatic tire in which one circumferential narrow groove having a narrow groove width is arranged.   2. The pneumatic tire according to claim 1, wherein a groove depth of the first lateral groove is partially shallowed in a boundary region between the inner groove portion and the outer groove portion of the first lateral groove.   If the inner groove portion of the first lateral groove is inclined toward one side in the tire circumferential direction from the first main groove toward the outer side in the tire width direction, the outer groove portion of the first lateral groove is extended to the circumferential narrow groove. 3. The pneumatic tire according to claim 1, wherein the pneumatic tire extends beyond the tire ground contact end from the circumferential narrow groove toward the other side in the tire circumferential direction toward the outer side in the tire width direction.   The pneumatic tire has a vehicle mounting direction specified, and the tread surface is located on the vehicle inner side of the tire equator when the tire is mounted, and the vehicle outer side is positioned on the outer side of the tire equator when the tire is mounted. The pneumatic tire according to any one of claims 1 to 3, further comprising a region, wherein the first main groove and the first lateral groove are disposed in a vehicle outer region of the tread surface. The pneumatic tire has a vehicle mounting direction specified, and the tread surface is located on the vehicle inner side of the tire equator when the tire is mounted, and the vehicle outer side is positioned on the outer side of the tire equator when the tire is mounted. Having a region, and arranging the first main groove and the first lateral groove in a vehicle outer region of the tread surface,
Two main grooves extending in the tire circumferential direction are provided in the vehicle inner side region of the tread surface, and the two main grooves are located in a range of 8% to 25% of the tire ground contact width from the tire equator surface. And a third main groove disposed on the outer side in the tire width direction from a region in the range of 8% to 25% of the tire ground contact width,
Between the second main groove and the third main groove, a second lateral groove extending from the second main groove toward the third main groove while inclining in the tire circumferential direction toward the outer side in the tire width direction is a tire circumferential direction. Arranged at a predetermined pitch, and a block is formed by the second main groove and the third main groove and the second lateral groove,
A third lateral groove extending beyond the other tire ground contact end while inclining in the tire circumferential direction from the third main groove toward the outer side in the tire width direction in the shoulder region on the outer side in the tire width direction from the third main groove. It is arranged at a predetermined pitch in the circumferential direction, and a block is formed by the third main groove and the third lateral groove,
The first main groove is disposed in a region located in a range of 8 to 25% of the tire ground contact width from the tire equator surface in the vehicle outer region of the tread surface, and the groove width of the first main groove is set to the second main groove. And the groove width of the narrower one of the third main grooves is 110% to 130% of the groove width,
Forming a center rib extending continuously in the tire circumferential direction between the first main groove and the second main groove;
The pneumatic tire according to claim 3, wherein the first lateral grooves are arranged at a pitch larger than the pitch of the third lateral grooves in the tire circumferential direction.   The pneumatic tire according to claim 5, wherein the groove width of the first lateral groove is wider than the groove width of the third lateral groove.   The pneumatic tire according to claim 5 or 6, wherein an inclination angle of the inner groove portion and the outer groove portion of the first lateral groove with respect to the tire circumferential direction is set to 30 ° to 85 ° on an acute angle side, respectively.   The pneumatic tire according to claim 5, 6 or 7, wherein an inclination angle of the third lateral groove with respect to the tire circumferential direction is 30 ° to 85 ° on an acute angle side.   The pneumatic tire according to claim 8, wherein the third lateral groove extends from the third main groove toward the outer side in the tire width direction and extends beyond the other tire ground contact end while being inclined toward one side in the tire circumferential direction.   The pneumatic tire according to claim 9, wherein the second lateral groove extends from the second main groove to the third main groove while being inclined outward in the tire width direction toward the other side in the tire circumferential direction.   The pneumatic tire according to any one of claims 5 to 10, wherein an inclination angle of the second lateral groove with respect to the tire circumferential direction is 30 ° to 85 ° on an acute angle side.   The second lateral grooves are arranged at a pitch twice that of the third lateral grooves, and the main grooves from one of the second main grooves and the third main grooves are directed in the same direction as the second horizontal grooves. While adjoining each of the second transverse grooves, one sub transverse groove extending at a tire width direction length of 20% to 80% of the tire width direction length between the second main groove and the third main groove is inclined. The pneumatic tire according to any one of claims 5 to 11, which is disposed between the pneumatic tires.   The pneumatic tire according to claim 12, wherein the auxiliary lateral groove extends from the third main groove.   The pneumatic according to any one of claims 5 to 13, wherein the center rib is provided with one narrow groove extending in the tire circumferential direction and having a groove width of 2 to 4 mm and a groove depth of 2 to 3 mm. tire.   The first lateral grooves are arranged at twice the pitch of the third lateral grooves, and extend from the first main grooves toward the outer side in the tire width direction between the adjacent first lateral grooves, and the groove widths from the first lateral grooves. The pneumatic tire according to any one of claims 5 to 14, wherein a narrow narrow lateral groove is disposed.   The depth is partially shallow in a region where the narrow lateral groove crosses the circumferential narrow groove, extends beyond one tire ground contact end, and the narrow lateral groove intersects the circumferential narrow groove. 15. The pneumatic tire according to 15.   The groove wall surfaces of the first main groove, the second main groove, and the third main groove are drawn at the intersections between the tread surface and the groove wall surface having an arc-shaped cross section in a cross section when the tire is cut along a plane passing through the tire axis. It is inclined with respect to a straight line perpendicular to the tangent line so as to pass through the intersection, and an inclination angle β1 of the groove wall surface of the first main groove with respect to the straight line is set to a groove wall surface of the second main groove and the third main groove. The pneumatic tire according to any one of claims 5 to 16, wherein the pneumatic tire is larger than an inclination angle β2 with respect to the straight line.

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